Remove support for Koka

Unfortunately, it is unusable due to excessive memory consumption. See
https://github.com/koka-lang/koka/issues/34.

This reverts commit 72c99b00c6.

backend/src/langs.ts

@@ -1422,19 +1422,6 @@ PLEASE GIVE UP
 `,
     timeout: 15,
   },
-  koka: {
-    aliases: ["kk"],
-    name: "Koka",
-    repl: "NODE_PATH=/opt/koka/node_modules rlwrap koka -i/opt/koka/lib",
-    main: "main.kk",
-    run:
-      "NODE_PATH=/opt/koka/node_modules rlwrap koka -i/opt/koka/lib main.kk; NODE_PATH=/opt/koka/node_modules rlwrap koka -i/opt/koka/lib",
-    template: `public fun main() : <div,console> ()
-{
-  println("Hello, world!")
-}
-`,
-  },
   kotlin: {
     aliases: ["kts", "kotlinc"],
     name: "Kotlin",

scripts/docker-install-phase3b.bash

@@ -64,9 +64,6 @@ default-jdk
 # Julia
 julia
 
-# Koka
-rlwrap
-
 # Ksh
 ksh
 

scripts/docker-install-phase6.bash

@@ -65,16 +65,6 @@ mv src-kalyn/Stdlib src-kalyn/Stdlib.kalyn /opt/kalyn/
 popd >/dev/null
 rm -rf kalyn
 
-# Koka
-git clone https://github.com/koka-lang/koka.git /opt/koka
-pushd /opt/koka >/dev/null
-npm install
-npm install jake
-npx jake compiler
-popd >/dev/null
-ln -s /opt/koka/out/debug/koka-* /usr/local/bin/koka
-rm -rf koka
-
 # LOLCODE
 git clone https://github.com/justinmeza/lci.git
 pushd lci >/dev/null